Transfers works only sometimes

I have installed Asterisk version 1.4.6 at two different sites.

My features.conf looks like the following:

parkext => 700 ; What extension to dial to park
parkpos => 701-720
context => parkedcalls
courtesytone = beep
transferdigittimeout => 3
xfersound = beep ; to indicate an attended transfer is complete
xferfailsound = beeperr ; to indicate a failed transfer
pickupexten = *9 ; Configure the pickup extension. (default is *8)
featuredigittimeout = 1500 ; Max time (ms) between digits for
; feature activation (default is 500 ms)
atxfernoanswertimeout = 15

blindxfer => 2#
atxfer => #

I also used the “tT” options in the dial command in extensions.conf

Sometimes the transfers works perfectly, other times you hear the “transfer” announcement, but when you enter digits, it does show the DTMF’s in the Asterisk CLI. As if the person did not press any digits at all. But the DTMF signals does work, otherwise you would not have heard the “transfer” announcement. This seems to be at random.

Both sites uses Snom 300, Snom 320 and Snom 360 phones. The Snom phones is also updated to the latest firmware versions.